Rotary piston machine

ABSTRACT

The invention relates to a rotary piston machine, comprising a housing ( 10 ) and a piston ( 12 ) which is situated in a hollow area of the housing ( 10 ) in such a way that it can rotate and which is rotationally fixed to a shaft ( 18 ) that passes through the housing ( 10 ). At least one inlet channel and at least one outlet channel for guiding a working fluid in or out of the hollow area are configured in the housing ( 10 ). According to the invention, the hollow area has a section which is configured in the form of a cylindrical ring cavity that is coaxial to the shaft ( 18 ). The piston ( 12 ), as a ring piston, is configured in the form of a cylindrical tubular section which engages in the ring cavity of the housing ( 10 ) and is axially displaceably guided in said ring cavity. The end surfaces ( 20,26 ) of the ring cavity and the ring piston ( 12 ) facing away towards each other are configured as constant wavy surfaces with an axially parallel amplitude. The inlet and outlet openings are located within an axial area of the lateral surface of the ring cavity that is determined by the maximum axial interval of the wave hollows of the end surfaces ( 20,26 ) facing towards each other.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicant hereby claims foreign priority benefits under 35 U.S.C. §119of German Patent Application No. 199 53 168.4 filed Nov. 4, 1999 and PCTApplication No. PCT/EP00/10831, filed Nov. 3, 2000, the disclosure ofwhich is herein incorporated by reference.

FIELD OF THE INVENTION

The invention concerns a rotary piston machine with a housing and apiston, which piston is rotatably arranged in a hollow space of thehousing and is rotatably fixedly connected with a shaft passing throughthe housing, with at least one inlet channel and one outlet channelbeing provided in the housing for the delivery and exhaust of a workingfluid to and from the hollow space.

BACKGROUND OF THE INVENTION

The invention has as its object the provision of a rotary piston machineof the above-mentioned kind which is of simple construction and in whichthe inlet and outlet openings for the working fluid can be controlled ina simple way.

SUMMARY OF THE INVENTION

This object is solved in accordance with the invention in that thehollow space has a section in the form of a cylindrical annular spaceco-axial to the shaft, that the piston is formed as a annular piston inthe shape of a cylindrical tube section which is received in the annularspace of the housing and is guided for axially shifting movement in theannular space of the housing, and in that the end surfaces of theannular space and of the annular piston which face one another areformed as continuous wave surfaces with amplitudes directed parallel tothe machine axis, so that the inlet and outlet openings lie inside of anaxial region of the lateral annular space surface, which region isdefined by the maximum axial spacing of the wave hollows of the endsurfaces facing one another.

The rotary piston machine according the invention can be driven as apump or, in so far as the wave surfaces of the annular space and of thering piston are formed with at least two wave crests and wave hollowsover 360° of the circumference, also as a motor. In general the machineis so formed that the housing remains stationary and the piston rotateswith the shaft. In principle, however, it is possible to also use theopposite arrangement, in which the housing rotates relative to thenon-rotating piston. However, in this case the connections for thedelivery and the exhaust of the working fluids become complicated. Thepiston can be axially slidably supported on the shaft or can be rigidlyconnected with the shaft, in which case the shaft is axially slidablysupported in the housing.

In the inventive solution, the working space of the rotary pistonmachine forms variable hollow spaces between the end surfaces of theannular space and of the annular piston which slide on one another. Eachhollow space expands or diminishes in size during the rotation and theaxial oscillating movement of the piston relative to the housing. Theinlet opening and outlet opening can be so arranged in the radiallyouter or radially inner lateral boundary surfaces of the annular spacethat they are cyclically opened and again closed by the piston wall, inorder in the case of a pump for example to suck in a working fluid andagain expel it, or in the case of a motor to suck in a fuel mixture, tocompress the mixture and subsequently to exhaust the combustion gases.

Since the annular piston is formed rotationally symmetrical with respectto its rotation axis, a completely smooth running of the piston isobtained. The same applies also in the case of a rotational housing. Noessential sealing problems appear. Movable valves for the opening andclosing of the inlet and outlet openings are not required.

Preferably the inlet opening and the outlet opening are so arranged thatin the circumferential direction one of the openings lies in front ofand the other lies behind a wave crest of the end surface of the annularspace. In this construction of the rotary piston machine as a motor, ona circumference of 360° one inlet opening and one outlet opening areprovided. In the construction of the rotary piston machine as a pumppreferably two inlet openings and two outlet openings are provided foreach end surface of the piston.

One of the end surfaces can be formed so as to have an at least nearlysinusoidal shape. The other end surface is preferably so designed thatan axial movement of the piston of maximum uniformity is achieved duringone revolution and no jerking or extreme acceleration of the piston inthe axial direction appears.

In a first embodiment of the invention the piston is biased in the axialdirection, for example by a spring, so that its end surface constantlylies on the end surface of the associated annular space. The force bywhich the surfaces are pressed together can also be regulated by thepressure fluid in the annular space.

In another embodiment, in a lateral surface of the piston or of theannular space a groove is formed in which is received a guide elementconnected to the other part (annular groove, piston), so that the pathof the groove in the circumferential direction corresponds to the waveshape of the end surface of the annular space. Thereby the translationalmovement of the piston and of the cylinder relative to one another iscontrolled by the groove. The end surfaces of the piston and the annularspace need not contact one another, so that wear of these surfaces bysliding on one another is avoided.

Another solution, for reducing the wear of the end surfaces by slidingfriction exists in that in one of the end surfaces of the annular spaceand piston facing one another, at least one guide element is rotatablysupported for rolling on the other end surface.

In a further embodiment of the invention, two annular space/annularpiston arrangements of the previously described kind are arrangedcoaxial to one another so that the two pistons arranged on the sameshaft move in common between the end surfaces of the two annular spaces.

For example, the two pistons can be unified into a one piece doublepiston. In this case the two end surfaces of the hollow space or of thetwo joined together hollow spaces are so arranged relative to oneanother that the maximums and minimums of their wave surfaces lie on thesame generatrix of the cylindrical lateral surface of the hollow space.Thereby it can be assured that the two end surfaces of the rotatingannular piston constantly slide uniformly on the two end surfaces of thehollow space when the piston rotates.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description explains the invention by way of exemplaryembodiments in connection with the accompanying drawings. The drawingsare:

FIG. 1 a schematic, perspective, partially broken away illustration of afirst embodiment of a rotary piston machine in accordance with theinvention with one piston/annular space arrangement,

FIG. 2 a sectional view containing the axis taken through the housing ofthe arrangement illustrated in FIG. 1,

FIG. 3. a schematic, perspective, partially broken away illustration ofa rotary piston machine with a double piston,

FIG. 4. a schematic, axis containing sectional view taken through thedouble-piston arrangement of FIG. 3,

FIG. 4a the detail A of FIG. 4 in an enlarged scale for a modifiedembodiment of the invention,

FIGS. 5-10 each a developed illustration of the end surfaces of thehousing hollow space and of the double piston which slide on one anotherof a double-piston machine according to FIGS. 3 and 4 operating as amotor, and

FIGS. 11-16 figures corresponding to FIGS. 5 to 10 illustrating adouble-piston machine which is driven as a pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The rotary piston machine illustrated in FIGS. 1 and 2 includes acylindrical housing 10 and a annular piston 12 made in the form of atubular section, which is rotable in an annular shaped hollow space 14of the cylindrical housing 10 and is guided so as to be axiallyshiftable. The piston is rotatably fixed to a shaft 18 by a radial base,which is indicated in FIG. 1 by broken lines at 16, or by radial spokes,but is axially shiftable on the shaft 18 which passes through thehousing 10. One such an axially shiftable and rotatably fixed connectioncan for example be achieved by way of splines, as illustrated in FIG. 4.

The annular space 14 has an annular shaped end surface 20, which canhave a straight or curved cross-section and which in the circumferentialdirection has a waved-shaped path with a wave amplitude parallel to themachine axis. As can be recognized from FIGS. 5-10, the wave path isnearly sinusoidal and in the illustrated example has two wave crests ormaximums 22 as well two wave hollows or minimums 24.

The front or end surface 26 of the annular piston 10 facing the endsurface 20 of the annular space 14 is likewise formed with a wave-shapedpath, as seen FIG. 1. This end surface also has two maximums or wavecrests 28 and two wave hollows 30 (FIGS. 5-10). This wave path is,however, so formed that the half width of a wave crest as measured inthe circumferential direction, that is, the width of a the wave crest inthe axial middle between one wave minimum and one wave maximum issmaller than the half width of a wave hollow. The arrangement can alsoselectively be reversed in so far as the end surface 26 of the annularpiston can be selected to be sinusoidal and the end surface 20 of theannular space 14 can have a smaller wave crests and wider wave hollows.

FIG. 2 shows further one of the inlet and outlet channels 32 in thehousing 10, which terminate at the inner boundary wall 15 of the annularspace of 14 and serve to deliver or carry away a working fluid to orfrom the annular space of 14, as is explained in more detail inconnection with FIGS. 5-16.

The piston 12 is biased by a helical spring 34 arranged coaxial to theshaft 18 against the end surface 20 of the annular space of 14. Insteadof the helical spring, a plate spring can also be used, which at thesame time can serve to connect the piston rotatably fast to the shaft.With such plate spring the axial construction length is shortened.

In the embodiment of the rotary piston machine according to theinvention illustrated in FIGS. 3 and 4, two piston/housing arrangementsof the type illustrated in FIG. 1 are arranged coaxial to one another,in which case the spring 34 is not present. The two pistons are unifiedinto a single double-piston, with similar parts in these figures beingdesignated with the same reference numbers as in FIGS. 1 and 2.

The arrangement of the end surfaces 20 of the annular spaces 14 is sochosen that the maxima and the minima of the two end faces 20 each lieon a common generatrix of the cylindrical annular space 14, as also seenin FIGS. 5 to 16.

The end surfaces 26 of the double-piston 12 on the other hand are soformed that the maximum or wave crest 28 of one end face lies in commonwith a minimum or wave hollow 30 of the opposite end face on ageneratrix of the cylindrical ring piston 12.

In FIG. 3 a guide groove formed in the radially outer wall of theannular space 14 is indicated at 33, which groove receives a pin 35fastened to the piston 12. The guide groove in its circumferentialdirection follows the wave shape of the end surface 20 and thereby socontrols the translation movement of the piston 12 without the endsurfaces 20 and 26 contacting one another. This solution is however onlyoptional.

FIG. 4 and FIG. 4a shows show yet another possibility for reducing thesliding friction between the end surfaces 20 and 26 and therewith thewear of these surfaces. In a recess in the end surface 26 of the piston12 a guide element 37 is rotatably supported so that it can roll on theend surface 20 of the annular space. 14.

FIGS. 5-12 concern a rotary piston machine of the type described inFIGS. 3 and 4 driven as a motor, with the functional explanation howeverlikewise applying for the machine according to FIGS. 1 and 2. Eachcylinder on a circumference of 360° is provided with one inlet opening36 and one outlet opening 38, and particularly in such a way, withreference to the circumferential direction of the piston 12 indicated bythe direction of the arrow A, that the outlet opening 38 is positionedin front of a wave crest 22 and the inlet opening 36 is positioned afterthe wave crest 22. The shape of the inlet opening 36 and of the outlet38 is in practice generally not circular but is shaped according to theapplication of the rotary piston machine and according to the type ofmedium flowing through the machine, in order to achieve an optimalcontrol of the medium flow.

FIG. 5 shows the piston 12 at its upper dead point. In this positionfour hollow spaces separate from one another are formed between theupper end surface 20 of the annular space 14 and the upper end surfaceof the piston 12. The hollow space lying between 90° and 180° contains amaximally compressed mixture at the time of ignition. The combustiongases are exhausted from the hollow space lying between 180° and 270°.The outlet opening 38 is closed. Upon a rotation of the piston 12 in thedirection of the arrow A, the inlet opening 36 is gradually opened sothat mixture is sucked into the hollow space lying between 270° and360°. On the other hand, in the lower half the ignition space defined inthe circumferential direction between 270° and 90° has reached itsmaximum expansion. The outlet opening 38 is opened. The piston 12 inrespect to its lower end surface 20 is located in its lower dead pointand the exhaust of the combustion gases from the combustion spacebegins. In the second hollow space lying between 90° and 270° themixture sucked in, which now upon further rotation of the piston becomescompressed.

FIG. 6 shows the previously indicated process with a rotation of thepiston 12 in the direction of the arrow A relative to the stationaryhousing 10. The upper inlet opening at 36 is now open, so that themixture can now be drawn in. The outlet opening 38 is closed. Thecombustion space is enlarging with the expanding combustion gases. Inthe lower portion, the outlet channel is entirely open so that thecombusted gases can be exhausted, while the inlet opening is closed andthereby a compression is possible in the involved region. FIG. 8 showsthe position inverse to that of FIG. 5, that is the piston 12 withrespect to the upper end surface 20 of the annular space 14 is in itslower dead point position and with respect to the lower end surface 20of the annular surface 14 is in its upper dead point position. At FIG.10 the condition illustrated in FIG. 5 begins again, at which the piston12 has carried out one revolution relative to the housing and therewithhas gone through the four steps of the motor, namely suction,compression, combustion and exhaust.

It will be recognized that it is possible to control the inlet andoutlet openings entirely without valves and by the piston itself, andthat except for the rotating and axially oscillating piston and theshaft, no further moveable parts are required. Especially no movablesealing elements are required. Since the piston is formed entirelysymmetrically, no unbalanced forces appear, to disturb the bearings orthe shaft.

FIGS. 11-16 show the same phases for a rotary piston machine formed as apump. Since in this case there are only two steps per work stroke,namely suction and exhaust, two pairs of inlet openings 36 (suctionconductors) and outlet openings 38 (pressure conductors) can beprovided. Moreover, the operating phases of the two piston/annular spacearrangements are again in the same way displaced 180° from one another,as has already been described for the case of the motor according toFIGS. 5-10.

It is claimed:
 1. A rotating piston machine with a housing (10) and apiston (12) which piston is rotatably arranged in a hollow space of thehousing (10) and is rotatably fixedly connected to a shaft (18) passingthrough the housing, with the housing (10) having at least one inlet andone outlet channel (32) for the delivery and exhaust of a working fluidto and from the hollow space, characterized in that the hollow space hasthe shape of a section of a cylindrical annular space (14) coaxial tothe shaft (18) and defined by a coaxially extending radially outerboundary wall and a coaxially extending radially inner boundary wall ofthe housing, that the piston (12) is formed as an annular piston in theshape of a cylindrical tube section, which piston is received in theannular space (14) of the housing (10) and is guided for axiallyshiftable movement, and that the end surfaces (20, 26) of the annularspace (14) and of the annular piston (12) which face one another areformed as continuous wave surfaces with amplitudes directed parallel tothe machine axis, wherein inlet and outlet openings (36,38) lie in atleast one of the boundary walls of the annular space, within an axialregion defined adjacent each axial end of the piston by the maximumaxial spacing of the end surfaces (20,26) facing one another.
 2. Arotary piston machine according to claim 1, further characterized inthat the continuous wave surfaces define at least two wave crests(22,28) and two wave hollows (24,30) for each 360° of the circumference,with the half width of the wave crests (38) measured in thecircumferential direction of at least one of the end surfaces beingsmaller than the wave hollows (30) of the same end surface.
 3. A rotarypiston machine according to claim 2, further characterized in that in acase of use of the machine as a pump at least two inlet openings (36)and two outlet openings (38) are provided for each end surface of thepiston (12).
 4. A rotary piston machine according to claim 1, furthercharacterized in that the piston (12) is axially slidably supported onthe shaft (18).
 5. A rotary piston machine according to claim 1, furthercharacterized in that the piston (12) is rigidly connected with theshaft (18) and that the shaft is axially slidably supported in thehousing (10).
 6. A rotary piston machine according to claim 1, furthercharacterized in that the piston (12) is biased in the direction towardthe end surface (20) of the annular space (14).
 7. A rotary pistonmachine according to claim 1, further characterized in that a groove(33) is formed in a lateral surface of the piston (12) or of the annularspace (14), in which groove is received a guide element (35) connectedto the other part (annular space 14, piston 12), with the path of thegroove in the circumferential direction corresponding to the wave shapeof the end surface (20) of the annular space (14).
 8. A rotary pistonmachine according to claim 1, further characterized in that in one ofthe end faces (20,26) of the annular space (14) and the piston (12) aguide element (37) is rotatably supported for rolling engagement on theother of the end surfaces.
 9. A rotary piston machine according to claim1, further characterized in that the inlet opening (36) and the outletopening (38) are arranged in the circumferential direction before andbehind a wave crest (22) in the end surface (20) of the annular space(14).
 10. A rotary piston machine according to claim 1, furthercharacterized in that the inlet opening and/or the outlet opening isprovided at the radially inner boundary wall (15) of the annular space(14).
 11. A rotary piston machine according to claim 1, furthercharacterized in that one of the end surfaces (20,26) which come incontact with one another is formed sinusoidally.
 12. A rotary pistonmachine according to claim 1, further characterized in that two annularspace/annular piston arrangements (14,12) according to claim 1 are soarranged relative to one another, that the two pistons arranged on thesame shaft (18) move in common between the end surfaces (20) of the twoannular spaces (14).
 13. A rotary piston machine according to claim 12,further characterized in that the two pistons are formed as a one piecedouble-piston (12).
 14. A rotary piston machine according to claim 12,further characterized in that the maximums and minimums of the twoidentically formed end surfaces (20) of the annular space (14) each lieon the same generatrix of the cylindrical lateral surface of the annularspace of (14), and in that the maximum (28) of one end surface (26) ofthe two pistons (12) lies in common with a minimum (30) of other endsurface (26) on a generatrix of the lateral surface of the piston.